Means for making concrete slabs



R. E. SMITH MEANS FOR MAKING CONCRETE SLABS Jan. 27, 1970 2 Sheets-Sheet 1 Filed Aug. 5, 1967 Jan. 27,1970 "RESMITH 3,491,680

MEANS FOR MAKING CONCRETE SLABS Filed Aug. 5, 1967 2 Sheets-Sheet 2 United States Patent MEANS FOR MAKING CONCRETE SLABS Robert E. Smith, Dayton, Ohio, assignor to The Flexicore Co., Inc., Montgomery County, Ohio,

a corporation of New York Filed Aug. 3, 1967, Ser. No. 658,108 Int. Cl. B28b 7/20 US. Cl. 25-41 2 Claims ABSTRACT OF THE DISCLOSURE The disclosure provides :a means for manufacturing concrete slabs having grout locking concave keys on the sides thereof in a casting form having a flat bottom and upstanding straight sides. At one or both sides of the casting form, after the mix is in place but prior to curing, a grout keyway of any desired shape is ploughed along the length of the casting form. The keyway thus formed in the mix may, if desired, be filled with inert material to maintain the keyway prior to curing. The casting form and contents are cured in conventional fashion.

This invention relates to a means for making concrete slabs having grout retaining concave keyways along one or both sides of each slab so that laterally adjacent slabs with registering keyways may be locked together by grout. Reinforced concrete slabs are widely used in constructing floors, ceilings and the like. Such slabs generally have longitudinal internal passages therethrough for the purpose of reducing weight and improving loadbearing characteristics. An example of a slab having such longitudinal passages is disclosed in United States Patent No. 2,299,070. In connection with the use of such slabs, concave keyways along each slab side are provided so that adjacent slabs with registering keyways may have grout poured into the keyways for locking adjacent slabs together.

For mechanical reasons, it is necessary that the keyways along the sides of slabs be so shaped as to lock the grout between such slabs against vertical removal. Where the slab is to be removed from the casting form by lifting the same from the bottom, the interlocking action between the keyway of the slab and the casting form side has created a serious problem. Thus, in Patent No. 2,614,309, removable liners for making keyways are provided. This permits the slab and liner portions to be removed simultaneously from a casting form having straight sides, Another expedient for providing for slab removal from a casting form is disclosed in Patent No. 3,023,477. This involves the control of the dimensions and shape of the slab keyway as well as the springing of the casting form sides and arching of the casting form bottom to permit removal of the slab. While this latter expedient is successful, the special steel and design of casting form and keyways has made such casting forms expensive to manufacture.

In accordance with the present invention, a simple casting form having a fiat bottom and substantially straight sides is used. The casting form may be of conventional grade steel and will normally have sufficient elasticity so that the form sides may be sprung slightly to release a casting. Any desired keyway shape may be adopted for one or both sides of the slab and a change in keyway shape will not involve any change in the casting form. A mix consisting of cement and aggregate is disposed in the casting form in conventional fashion and may be vibrated to remove air and effect compacting. Thereafter and in accordance with the invention, a desired keyway is ploughed out from the mix along one or both sides of the casting form to provide a til) desired keyway in one or both sides of the slab to be cast.

Preferably a low slump mix having maximum stiffness is used for casting so that a ploughed keyway will remain intact until the slab is cured. The stiffness of the mix may be reduced and the keyway may be temporarily supported by filling with dry sand or other dry inert material, which will separate from the slab proper after curing and removal from the form.

The advantages of the invention are manifold. Since the casting itself is smooth, the fabricating cost is substantially reduced over keyways having especially shaped sides for producing a keyway. In addition, the casting form may be of mild steel which is more readily obtainable than high tensile stress variety necessary for some kinds of forms and the mild steel has a better surface finish. Slabs of various depths may be cast with the same casting form. In addition, narrow slabs can be cast, this being difficult with high stress steel forms incorporating integral grout keys. Another advantage is that the smooth casting form sides and bottom may be cleaned easily after a casting operation.

The invention will now be described in connection with the drawings wherein FIG. 1 shows a plan view of a machine embodying the invention.

FIG. 2 is a side elevation partly in section of the machine illustrated in FIG. 1.

FIG. 3 is an end elevation of the machine, certain parts broken away for clarity.

FIG. 4 is an exploded view of the plough and screed sub-assemblies detached from the screed vibrating frame.

FIG. 5 is a detail of a portion of the casting form showing an end bulkhead and plough.

Casting form 10 'for use with the machine illustrated in the drawing has a U shape consisting of bottom 12 and sides 14 and 15 extending straight upwardly therefrom. The entire casting form may be made in any desired length. Thus, casting forms referred to in the patents previously identified may have a length of the order of from 30 to 60 feet. Insofar as the present invention is concerned, the casting form may have an indefinite length. Such lengths of slab may thereafter be sawed to standard lengths or the casting region may be subdivided into desired lengths.

Casting form 10 may be of any suitable material and when the casting form itself is transported or moved from one location to another, it is desirable to make the casting form of steel. Since the casting form sides 14 and 15 are smooth and since castings may be removed from the form with little, if any, spreading of sides 14 and 15, mild steel may be used.

Where the casting form is handled and moved about, it is desirable to reinforce the casting form sides by steel channels 17 and 18 whose webs are secured to the outer surfaces of the casting form in any suitable fashion, as by welding. Channels 17 and 18 have the flanges thereof extending laterally outwardly from the casting form and for convenience the bottom flanges of channels 17 and 18 may be level with the bottom outer surface. This permits a casting form to travel along a suitable conveyor. The conveyor may be of any type and may have rollers 22 (some or all being power driven) at intervals along which a casting form may travel. To further guide the casting form accurately along the conveyor at a ploughing station, guide rolls 23 and 24 are provided for engaging the outer edges of the bottom flanges of channels 17 and 18. Rollers 23 and 24 may be rubber and are supported on rigid standards 25 and 26. Standards 25 and 26 are located at the ploughing station to be described and carry posts 27 and 28 for adjustable supporting of a super-structure at the ploughing station. The

conveyor itself may be provided with means for adjusting the elevation thereof.

In the mechanism to be described, the ploughing station is, relative to the casting form, stationary with the casting form passing through the ploughing station. It is possible to have the ploughing station movable and have a stationary casting form of indefinite length. The objective is to obtain relative motion between the casting form and ploughing station longitudinally of the casting form.

The casting form, whatever its length, will be provided with bulkheads at the ends of the casting form and at any intermediate places along the casting form as desired. Such bulkheads are of well-known construction and may have holes therethrough for accommodating inflatable cores. Such cores are used to provide longitudinal voids or passages through the length of a slab to improve the load-bearing characteristics of the slab as well as save on concrete. In addition, pre-stressing steel strands may be provided with such strands passing through bulkheads and having suitable means for maintaining tension. Thus, in United States Patent No. 3,207,829 a bulkhead construction is disclosed for accommodating inflatable cores and pre-stressing strands. The invention is not concerned with the details of bulkheads and with pre-stressing.

As is well-known in this art, a casting form of desired shape and length is filled with a mix of cement and aggregate in desired proportions. For the purposes of this invention, the mix is preferably quite stiff and has low slump. Such a mix has suflicient water to support the chemical interaction incident to setting of concrete but preferably has minimum excess water. It is conventional practice in this art to subject the mix to vibration for the purpose of removing air bubbles and settling the mix in the casting form. The present invention involving ploughing keyways in the mix is useful after a casting form has been filled with mix and has been vibrated but before curing.

After the ploughing operation to be described, the mix in the casting form is allowed to cure. Where the casting form is transportable, the casting form and mix are disposed in a steam room where a temperature of about 135 F. is maintained so that accelerated curing takes place. Where a casting form of indefinite length is used and is not transportable, the curing action may be allowed to take place under normal outdoor conditions. Such concrete may be covered with material such as straw or paper to prevent excessive loss of water.

The ploughing station (whether stationary with a casting form movable through the same or movable with respect to a stationary casting form) comprises basically two component sub-assemblies. One sub-assembly consists of two ploughs, 31 and 32, rigidly secured by upwardly extending post portions 33 to 36 inclusive to cross strips 37 and 38. The assembly may be of metal. Ploughs 31 and 32 have a cross-sectional shape for providing the desired keyway and may have a length of about 2 or 3 feet. This dimension is not critical and, as a rule, may vary within Wide limits. Plough portions 31 and 32 have top edges 40 and 41.

These ploughs will be disposed so that they can slide along the inside surfaces of the casting form sides at a prescribed elevation with respect to the casting form bottom. The elevation may be adjusted by the structure hereinafter described so that a range of desired thicknesses of slab may be cast in the same casting form. A transverse separation of ploughs 31 and 32 will be determined by the Width of the casting to be made. In some instances it may be possible to have a false casting form side for arbitrarily reducing the transverse width of the casting region in which case ploughs 31 and 32 will be spaced appropriately.

Cooperating with the plough sub-assembly is a screed sub-assembly consisting of flat screed plate 44 bounded on the sides and trailing end by vertical bin sides 45, 46 and 47. Screed plate 44 has a tapered bottom front edge 48 of generally V shape extending rearwardly. Screed plate 44 has a smooth bottom face of steel. Bin side walls 45 and 47 have their bottom edges normally disposed just above top edges 40 and 41 of the plough sub-assembly. The outside width of the screen sub-assembly (across walls 45 and 47) is such that this sub-assembly fits snugly against the inside faces of the casting form sides unless the screed sub-assembly is near the top of the casting form. The transverse dimension of screed plate 44 including the thickness of walls 45 and 47 is equal tothe separation of the outer surfaces of the plough sub-assembly at plough portions 31 and 32. Rigidly attached on the inside to the open-ended bin formed by screed plate 44 and side walls 45, 46 and 47, are vertical posts 50 to 53 inclusive secured to generally rectangular vibratory frame 56. Frame 56 carries rollers 58 along the sides. Rollers 58 are adapted to operate in short guides 60 and 61 carried by stationary frame 62 surrounding vibratory screed frame 56. The construction is such that vibratory screed frame 56 is supported by stationary frame 62 for vibration between front and rear walls 63 and 64 of frame 62, this being along the direction of movement of the casting form relative to the ploughing station. The movement of the screed plate and bin (formed by walls 45, 46 and 47 will generally have an amplitude of about 1 or 2 inches and the oscillation of this screed will be at a rate of about to 200 per minute. The amplitude and rate of oscillation may vary within wide limits.

The V shaped edge 48 of screed plate 44 and the forward edges of bin sides 45 and 47 are tapered to provide a sharp edge. The sharp edge in the case of the V for screed plate 44 will be down against the surface of the mix. The sharp edges for sides 45 and 47 will be against the casting form sides in the event that the screed subassembly rides low enough in the casting form to engage the casting form inner surfaces.

The plough sub-assembly is supported from stationary frame 62 by cross-members 37 and 38 attached thereto and the two sub-assemblies are supported at a desired elevation with respect to casting form bottom 12 in any suitable fashion. Thus, support frame 62 has blocks 67 for clamping to vertical stationary posts 27 and 28. Vibration of the screed sub-assembly longitudinally of the casting form is obtained by motor 70 (air or electric) coupled to vibratable frame 56 by suitable means. Thus, a tongue and fork arrangement between oscillating motor 70 suitably anchored and frame 56 is illustrated.

The leading portions of ploughs 31 and 32 are forwardly of screed plate edge 47 and the V shape guides ploughed up mix material toward the center portion of the screed plate edge. The rapid vibration of the screed plate tends to work the mix material displaced by ploughs 31 and 32 from the top surface of the uncured slab. Bin walls 45, 46 and 47 provide a storage region for ploughed up mix material with the longitudinal vibration of the screed plate tending to work the excess mix from the top surface of the body of the mix in the casting form on to the screed plate. The various portions of the mechanism may be made of suitable materials such as aluminum, steel, or any other metal. By controlling the mix level in a casting form prior to ploughing, the final level after ploughing and screeding can be the desired level for casting, with excess mix being collected and retained by bin wall 45, 46 and 47 and the screed plate.

As a rule, with a stiff mix, the ploughed mix along the casting form sides will retain its shape and maintain the keyway. In the event that it is desired to use a mix which has less stiffness or if it is desired to insure against mix caving in and destroying the ploughed keyway, it is possible to fill the ploughed keyway with sand or other granular inert material up to the desired level in the casting form. This may be accomplished by having spouts 75 and 76 disposed above the casting form to feed such sand to a ploughed keyway immediately after the ploughing operation.

Some provision must be made for accommodating bulkheads extending across a casting form at the ends or intermediate regions. It is possible to have key slots 77 cut in a bulkhead at the appropriate parts thereof for clearing ploughs 31 and 32. This arrangement is illustrated in FIG. 5. In FIG. 5, a plough is shown as having a portion of the length of simple rectangular cross-section ar d a different portion provided with a block for shaping the keyway to the exact shape desired. By having a plough accommodating slots in bulkheads, continuous travel between a ploughing head and a casting form over the entire length of a casting form can be accomplished.

It is possible to use bulkheads not having keyway accommodating slots and stop the ploughing operation when a plough reaches a bulkhead. The entire ploughing mechanism may be elevated (or the casting form may be dropped) so that ploughs 31 and 32 will clear the tops of the bulkheads. The reverse procedure can be utilized at the beginning of a ploughing operation where the bulkheads will not accommodate ploughs 31 and 32. In such case, the procedure will be to drop the entire plough means (or elevate the casting form and mix) so that the ploughs are disposed in proper position in the mix.

In those instances where vertical clearance between ploughs and bulkheads must be provided, due to the absence of key slots in bulkheads, it is not essential to extend the keyways to the very ends of a slab. A finished slab when installed will have its ends supported by rigid means. The unsupported slab lengths between the end portions of the slab usually require the keyways for grouting to prevent difierences in sag between adjacent slabs.

It is possible to reduce the mechanical load on the ploughs by making a preliminary ploughing of the mix as the casting form reaches the ploughing station. To this end, discs 80 and 81 secured on shaft 82 extending transversely above a casting form are provided. Discs 80 and 81 are rotated rapidly by electric motor 83 driving sprocket chain 84 for rotating shaft 82. Discs 80 and 81 are,located adjacent the sides of a casting form where a grout key is to be provided and have the peripheral portions so shaped that a substantial portion of mix is removed just prior to reaching the ploughing region. It is understood that the peripheral shape of discs 80 and 81 is selected so that the plough itself can still provide a properly shaped grout key.

It is understood that after a mix has been ploughed, the mix in the casting form is allowed to cure. Generally, for ease in slab removal after curing, the casting surfaces in a form are first thoroughly cleaned and oiled. The cured concrete does not adhere to an oiled surface and consequently permits the ready removal of a slab from a casting form.

The invention simplifies conventional manufacture of slabs in casting forms and the changes in equipment and procedure for utilizing the invention are in the direction of simplicity and economy.

What is claimed is:

1. In a facility for casting a long concrete slab having a length of a higher order than slab width or thickness and Where a cast slab has a concave key longitudinally thereof along each slab side, a structure for operating in conjunction with a casting form having a flat bottom and straight upstanding sides and no top, said structure functioning to shape those portions of mix within a casting form which will provide the concave keys in the casting, said stucture containing a plough for each casting form side, each plough having a cross sectional shape corresponding to the desired key, each plough having a length short in comparison to a casting form length, each plough including a side wall portion extending above the plough portion proper, a flat screed plate extending between the bottom parts of said side wall portions, said screed plate having front and rear edge portions transversely of said casting form length, a rear side wall portion extending at the rear screed plate edge upwardly to form a three sided bin with the screed plate and two side walls, the forward edges of the side Walls and screed plate being tapered to guide mix generally to the bin interior, a rectangular inner frame rigidly secured to said bin side walls above the top of said bin, said inner frame and ploughs and bin walls and screed plate being rigidly secured together, an outer frame disposed about the inner frame, means on said two frames for supporting said inner frame within said outer frame to permit limited movement of said inner frame within said outer frame only in a direction longitudinally of said casting form, means for supporting said outer frame in fixed position above a casting form with said ploughs at a level where such ploughs would be at a desired distance above a casting form bot- ,tom, means for vibrating said inner frame in the direction provided by the frame supporting means, and means to provide relative continuous travel between a casting form containing mix and the frames with bin and ploughs in proper direction against the screed front edge.

2. The construction according to claim 1 wherein a rotatable disc is provided ahead of each plough with each disc having its edge in line with each plough, said discs being rotatable about a common axis transverse to the length of a casting form and the disc edges being shaped to remove a substantial portion of mix to be removed by the ploughs for providing keys.

References Cited UNITED STATES PATENTS 2,970,361 2/1961 Brown 2599 3,217,375 11/1965 Kinnal'd 2541 J. SPENCER OVERHOLSER, Primary Examiner DEWALDEN W. JONES, Assistant Examiner 

